Simplify the following expression: ${-8r-1-r-8}$
Solution: Rewrite the expression to group the ${r}$ terms and numeric terms: $ {-8r - r} {-1 - 8}$ Combine the ${r}$ terms: $ {-9r} {-1 - 8}$ Combine the numeric terms: $ {-9r} {-9}$ The simplified expression is $-9r-9$